Assemble
by moriartysfallenangels
Summary: The Avengers are pulling out all the stops to defeat a new evil, the Shadow. They need a bit more than their usual team. Special thanks to HumanitiesBest for helping me out!
1. Chapter 1

**A/N: Hello! I've now posted 7 chapters, so this author's note is something I'm adding for a SPECIAL REASON.**

 **Humanities. Best made me a trailer! AND MY COVERART AAHHHHHHH. Yeah hot-topical-cas made that. So much love.**

 **I can't link it, which is sad. It's also hard to find which is sad. *holds back a rant so people don't hate me***

 **Oh, well. This author's note is basically pointless. Enjoy the fic!**

* * *

" _Humans are odd. They think order and chaos are somehow opposites and try to control what won't be." -Vision_

* * *

 **Present Day**

 _"We can't do this alone," Steve argued. "This threat is bigger than Loki, bigger than Ultron! We need all the help we can get."_

 _"I've told you a thousand times, Gramps," Tony replied. "The Instant Project is nowhere near finished. For a human to test it out now would be catastrophic, like all of time and space collapsing catastrophic. This is dangerous stuff I'm tampering with."_

 _"You're not normally this cautious about your projects," Steve said, defeated._

 _"Well this one could not only destroy the world, it could destroy the entire galaxy. All just to defeat one woman."_

 _"She's not just any woman. She's the Shadow."_

* * *

 **1947 (Two years after WWII ends)**

It was a warm summer night in Brooklyn. The lights on the streets were dim, and music was playing throughout the block. A party was going on, and the melody from Glen Miller's "In the Mood" drifted up from the streets below into the office of Peggy Carter. Peggy sat alone in the room reminiscing about what had happened in the past year. Along with the help of Edwin Jarvis, they had cleared Howard Stark's name. She had also been appointed as Co-Director of SHIELD, a branch off of the SSR. where she had been assigned after showing off her skills in the field. It may have been small, but Howard and Peggy had it up and fully functional in a matter of a few months.

Jarvis had come to check on Peggy not too long before. He had noticed earlier that year, that Peggy was not a person who was fond of big parties. She would make her appearance with Howard, and then slip quietly away into the crowd, eventually leaving it completely when everyone was too tipsy to notice. Since Jarvis usually had to take Howard home, he didn't drink at all. Sometimes they would leave together and they would trade stories, or just talk. It was one of Howard Stark's parties that night, yet, Peggy didn't have any intentions of making an appearance at all. Apparently, she still was doing _all_ the filing in the agency. With that, she decided to work late that night to refile the archives.

It wasn't that long later when Peggy stumbled upon the Project Rebirth files. She found various mix-matched inventions Howard had thrown in there yet _again._ She quickly flipped through them, seeing some that she'd like to erase from her memory when she happened upon a manilla envelope titled: The Instant Project. Inside were indepth blueprints that Peggy was unable to comprehend. However, at the beginning, there was a summary of the project and details of the testing Howard had conducted. The files had apparently been hidden so that no one would stumble upon them, but Peggy had. The summary included in depth details of a prototype of a machine designed to travel in time. After comprehensive testing, the subject perished and the Project was instantly cut off. That must be why Howard hadn't been working on his inventions as much lately, this had happened recently.

Immediately after this discovery, a loud sound indicated the activation of the elevator. She heard the creaks and groans the elevator makes when it's preparing to come to her floor, on the third level. Peggy immediately sprang into action, hiding behind the filing cabinets and grabbing the first solid thing that was on the table behind her, which just so happened to be a stapler. The elevator sounded when it reached the floor of the current SHIELD headquarters and Peggy tried to make out a silhouette in the darkness of whoever stepped out. She heard him step out and saw him pull out something out of jacket pocket, most likely a gun. Peggy was unable to see around the corner without giving up her position. She listened for the footsteps of the man to come around the corner but she only heard a strange warble coming from his direction. She focused all of her attention on listening on him, like she had been trained. She heard the man's cautious footsteps as he made his way around the level. As soon as he came looking around the corner, her foot immediately went out and kicked him behind his knee. The man cried out and a metal stick flew from his hand. Peggy stood up and grabbed the man by the collar to see his face, because no one was supposed to be back and she didn't want to seriously injure Howard or Jarvis, that would be bad. However, the scrawny man below her was a stranger, but he didn't fight back.

"Hello, uh, I'm the Doctor," he offered, understanding that she was friendly unless provoked.

"Doctor who?" she asked in a similar accent.

"Ah British!" He said, seemingly pleased. "I've been dealing with Americans for days! I'm the Doctor and that's all you'll ever need to know."

"If you want to leave here alive, you're going to have to provide a bit more than your title, Doctor," she threatened.

"Okay, well, you see...uh…" he searched for proper words to give Peggy. "I'm looking for Peggy Carter."

"What do you want with her?" She replied a bit too quickly and she tightened her grip on his collar.

"You know her? Do you know where she is?" The Doctor pressed. "You see it's...complicated."

"I've got time."

"Captain America needs her assistance."


	2. Chapter 2

" _We could at least contact Coulson and his team and the remaining bit of SHIELD," Steve continued to argue with Tony on the topic. He knew how cocky the man beyond the suit could be. "Shadow is getting stronger and this is more than we can deal with."_

 _Tony stared at the remains of his father's project that had been started back in 1947 and he looked back at the prototype that he built, mimicking the patterns but with more advanced technology that could potentially build the first time machine. He thought over Shadow and what she was capable of. She destroyed worlds, hell she destroyed galaxies._

" _JARVIS call Lazarus, please," Tony said to the room._

" _Do you mean Phil Coulson, sir" Jarvis replied._

" _Yes, JARVIS," Tony replied slightly annoyed._

" _Contacting: Phil Coulson."_

 _On the screen, a picture of Phil Coulson popped up and JARVIS began to connect them to the man himself. After a few seconds of ringing, a live chat popped up and Phil Coulson along with Melinda May filled the screen._

" _Hello, Mr. Stark, Mr. Rogers, what do you have for me?" Coulson asked with a clearly agitated May next to him._

" _What do you know about the Shadow?" Steve asked._

" _I know that she believes in a pure Earth." Coulson finally realized what this was about. "She believes only the dark belong here, those with dark hearts. Don't know how she determines who has a dark heart. I've been getting reports of sightings. Is she really back?"_

" _Afraid so," Steve said._

" _Then it's time to call them in," Coulson smiled, he almost seemed excited. "May, will you get the Avengers Expansion files?"_

 _She left the screen without a word._

" _Tony, how is the Instant Project coming along?"_

" _It's going somewhere, don't know where that is, but it's nowhere near ready to be put into use," Tony responded._

" _Then we need to call our… special advocate for the Avenger Expansion before we even retrieve some of the other Avengers-soon-to-be." Coulson said. "We need the Doctor."_

* * *

 **1947**

 _Steve._

"Nice try, but Steve Rogers is dead," Peggy said, holding back her emotions so maybe she could fool this man into thinking she wasn't Peggy Carter. "He died almost two years ago."

"You mean he froze almost two years ago," the Doctor replied.

"Same thing, he's still gone."

"Not in the future," the Doctor replied with a smirk. He was obviously seeing right through her. His eyes seemed so old and knowledgeable, it wasn't surprising.

"What?" Peggy let go of the Doctor's collar and let him stand up. "What do you mean in the future? Time travel isn't possible."

"For humans it isn't but I happen to be very, very not human." This then caused Peggy to be suspicious of him, but due to her history, she knew not to shoot first and ask questions later. So she went with it.

"Explain." At this word, the Doctor got very excited and began to walk towards the elevator.

"How about I show you?"

Peggy watched him walk to the elevator, begrudgingly decided to followed him, and got in. She quickly pressed the worn button for the ground floor and they rode down in an awkward silence. Then the elevator reached the ground floor and relieved them both. The Doctor was never fond of those that battled him for authority but he liked the way this woman did it. She wasn't rude, just protective of everything she had established and that included the rest of the human race. They walked out the door of the office building and onto the sidewalk.

"Doctor, where exactly are we going?" She knew it wasn't smart to just follow this man around, it still could be a trap.

"We're almost there." This confused Peggy because there was nothing around, only sketchy shops with not so pleasant people around them. "Here we are."

Peggy looked at what he was pointing to and saw a big, indescribably blue blue box with "Police Public Call Box" written at the top. She didn't understand.

"And?" She tried to act unamused but she was incredibly intrigued at the level of madness the man had achieved. He actually seemed a bit hurt.

"It's a TARDIS! She's lovely and she can take you anywhere in time and space," he then began muttering something to box, not helping his case.

"Prove it then," Peggy said. The Doctor smirked and unlocked the door. He pushed it in and a slight cool draft blew out. Peggy gazed inside and saw a world she never could have imagined. It was larger on the inside, an impossible feat that could only be achieved in the future or by someone from another planet. The walls had lights that were brighter than any she had ever seen, not even Howard could make them glow that bright. In the middle was a console with more options than possibly imaginable. It was beautifully terrifying knowing that this sort of technology existed out of the reach of the SSR and SHIELD.

"Well?" The Doctor proudly asked.

"Take me to Steve."


	3. Chapter 3

**Present Day**

Captain Steve Rogers was pacing back and forth between two counters in the lab of Tony Stark, while rubbing the back of his neck. It was a common thing he did while under stress, which was an almost constant thing. Coulson remained on the screen, sifting through piles of files with Melinda May in and out of view in the background. They were looking for a well hidden file that contained lists of people that could be trusted and who could be useful in situations such as the one beginning to play out. The list contained enhanced, inhumans, and just generally brilliant people. It didn't discriminate.

Steve then broke the silence that filled the lab. "How do we even contact him? What if he doesn't want to help us out?"

"I know the Doctor," Coulson replied without looking up. "And I know he won't leave Earth without making sure the Shadow is contained again."

"I've got it," Agent May declared and showed Coulson a dark gray file with a large SHIELD emblem on the front, like most of the others. "Uh… Coulson?"

"What?"

"Why is Agent Carter listed? She isn't exactly…" May searched for the proper words to say about the co-founder of the association she worked for. "...Ready to fight."

"The Doctor is a time traveler. Come on May, brush up on your aliens." May returned his comment with her signature glare of death.

Everyone forgot what Peggy meant to Steve. Or maybe they never knew. They certainly didn't notice when Steve blacked out for a moment. The dream that Wanda put in his mind during a battle against Ultron returned to his memory. The flashing lights that made his blood pound even louder in his enhanced ears. The soldiers out of place amongst the ones that Steve gave up everything to protect. All of them were so happy, covered in blood, holding drinks and laughing. Then she appeared and he say nothing else. She was the most beautiful woman he had ever met. Peggy saw him before he had muscle, she loved him for his heart which was all he ever wanted.

A loud bang resonated through the lab, bringing Steve back to reality. Tony had dropped a wrench while in an argument with May and Coulson. Steve began to tune into what they were saying.

"She is a very important asset in this fight and as director of SHIELD I overrule you," Coulson asserted. "Contact the Doctor and have him bring her to this time. Give him these space time coordinates." Coulson clicked a button and a flashing mail sign appeared in the corner of the screen.

Tony ignored it and instantly replied, "What if she dies?" Coulson and May both stopped what they were doing. "Huh? What then. SHIELD will never take off because I assume you're going to get her from 1947."

"Well, yeah," Coulson ignored his testy tone. "She's most likely to come with us at this time and-"

Tony banged his fist on the table, interrupting Coulson, "You just don't get it!"

"Then explain it to me, Mr. Stark."

"The Instant Project is touchy! I don't want something bad to happen to her and my memories of her being gone!" Tony glared at the director of SHIELD expecting him to understand, as he had had his memories tampered with. Yes, differently, but tampered all the same.

Everyone went silent. Coulson and May looked at each other and waited for Tony to break the silence. Steve's blood ran cold at the thought of seeing her again. He knew it was wrong. It was definitely not the natural order of things. Tony's outburst made Steve's longing go away at the worry of losing her again. But, he knew she had valuable information and skills that they needed.

"Tony," Steve's voice slightly cracked, he internally cringed. The man looked at him in shock. "I completely agree with you, but we need her."

"Fine. Fine. Let's destroy the universe shall we?" Tony ran around his lab pressing buttons and checking charts. He then walked over to a large switch, tucked off to the side of the entire room. Tony glanced up at Steve Rogers for a split second before smirking and forcefully pulling the lever. The sound of a phone ringing filled the room and the number "07700 900461" appeared on Tony's largest screen, next to where they had been talking to Coulson.

Jarvis then startled Steve, who still hadn't yet adjusted to the A.I., and said, "Now calling 'The Doctor'." Tony looked over to the Captain with a victorious smile. Coulson and May stood by, in view on the screen. Steve's blood pounded in his head.

"Tony," Steve asked. "The Instant Project is just a machine to call a time traveler?"

"Yeah. I tweaked my father's design. He didn't have the knowledge of quantum physics that we do today." The strange wheezing and groaning of the TARDIS faded in as it landed across the room. The blue box was bluer than ever and the slight thud of it sounded was it completely materialized. The door slowly opened and creaked as it did so. The agents and avengers stared at the box surprised that Tony's machine worked. The room was silent as a face cautiously appeared from the door, peeking out and checking the environment.

Then in a split second, he opened the door and stepped out to face the group.

"Doctor," Coulson caught his attention, but the Doctor didn't allow him to continue.

"Do you have any idea what you just did?" They all looked at each other in unison, equally confused at the question. "I was in London with my two friends. Then I went back inside my TARDIS and it took off without me authorizing it. Leaving them behind maybe stranded until I get back." He had made his way around the lab poking at things and generally amusing himself until he came upon the switch.

"Doctor," Coulson started again but the Doctor cut him off.

"Phillip J. Coulson you know I told you never to call me again!" The Doctor didn't even look at Coulson. He was too occupied with the large switch in front of him. "Tony Stark, you never seem to astound me. Your father made this, didn't he?"

"Yeah...uh," Tony stammered out, still in shock his machine was successful.

"Doctor…" Steve said.

"What does everyone so desperately want me to know?"

"The Shadow is back and we need you to gather a few people to help stop her again. It's much worse this time," Coulson finally got out. The Doctor turned around and looked at the group again, with a grim look on his face. He finally was getting the picture.

"Who do you need me to get?"


	4. Chapter 4

This wasn't the Doctor's first rodeo. For the Battle of Demon's Run, he had collected a group of allies that helped him defeat Madame Kovarian. Now he had to collect a group of extraordinary humans to defeat an old enemy. He first encountered the Shadow with a younger face, his tenth to be precise. She was about an equal to the Daleks; she was difficult to defeat but it wasn't impossible. The Doctor contained her on an island that he managed to completely cover in a magnetic field that she couldn't leave. Her escape was terrifying to the Doctor, because that meant she was very powerful.

The list was strange. He didn't recognize some of the people but there were short descriptions for when he went to retrieve them. There were more Americans than the Doctor cared to deal with, but he knew he would need help and he couldn't afford the time to make his own list. Coulson was sending his team on a plane to the Avengers tower for even more help, so there would be more people for him to meet. He didn't know how he felt about that.

The first one on the list was the only one that he had to travel in time for, Peggy Carter. He knew why she was listed, she had dealt with the Shadow and remembered her weaknesses. She wouldn't remember the Doctor, and not just because he had a different face. The woman wasn't like other soldiers he had met, she hardly knew the Doctor and she sacrificed herself to save him. He had planned to absorb some of the time vortex and take out both the Shadow and himself to save his favorite planet. The time arose for him to finally go through with his plan, but Peggy Carter tied him up and did it herself so he would survive. She was strong, but not strong enough to hold the time vortex. She nearly died like Rose and Donna before her. The Doctor was able to contain it, but she wouldn't remember much of what she did and what she sacrificed, which slightly saddened the Doctor. They had actually become good friends. He wanted her to come with him. She probably wouldn't have accepted anyway.

Anyways.

The Doctor landed in 1947 and heard the poppy '40s beat of "In the Mood" float through the door of the TARDIS. He stepped out the door and a grand party stretched before him. He was never really one for parties, though he did like the dancing. He soon located the drab building that hardly stood out from the others, perfect for a top secret organization. It had a total of four floors, not sticking out from the other buildings The music faded as he unlocked the door with his sonic screwdriver and accessed the elevator, screwdriver still in hand. Listening to the creaks and groans of the elevator, he put away his screwdriver again and fixed his suspenders, in a nervous gesture. He went up to the third floor and the elevator dinged, making the Doctor slightly cringe at the thought of what the agent-now director of SHIELD-was capable of.

The floor was dark, but he could sense that someone was here. Pulling out his sonic screwdriver, he went around the room to see if he could at least figure out where the agent lived, since she may not be at her work. There were tall stacks of papers on every desk, including one off of the others in a room with walls made completely of glass. He decided to start investigating there. Throughout all of time and space he had encountered many different people of different races, species, and personalities. But never did the Doctor think he would be attacked by a stapler on the way over to her office. Peggy Carter was a very cautious and guarded woman, but when Steve was brought into the equation, she would definitely come. And she did.

* * *

The TARDIS would be very full during this journey, but the Doctor insisted on bringing everyone to the Avengers tower at once. The next person-people-on the list were located in a top secret bunker in Lebanon, Kansas. The paper had a small description next to the coordinates that read: **Warning: Possibly aggressive and/or temperamental.**

 _Where does Coulson find these people?_

Nevertheless, the Doctor continued on with his mission and traveled back to the time the Avengers were in with Peggy Carter staring in awe at his TARDIS the entire time. She was constantly analyzing and calculating, trying to figure out all of the new information given to her. The room shook as the TARDIS flew and then landed with a ding.

"Peggy, I can call you Peggy, right?"

"Sure," she replied, still in awe and a bit breathless from the ride.

"You stay here, I have to pick up more people and I've been informed that the less people the better with these two," the Doctor requested as he adjusted the sleeves of his coat. "Only a few more after them and then… yeah."

"You've been very vague, Doctor," she said with a slightly accusational tone.

"I know." He approached the woman and said with all of the honesty and sincerity he could muster, "I know how much you want to see him, believe me I do, and you will."

He walked towards the door but paused before looking back at her with his signature giddy smile. Peggy Carter slightly smirked, making the Doctor feel a little bit more comfortable about the situation he was about to walk into. Stepping out of the TARDIS, he noticed a vast library with tables sitting in the middle of the room. Across the hall was a gigantic telescope that the Doctor instantly wanted to investigate. Right as he was about to explore, the voices of two men arguing could be heard from his place in the library, sending a nervous jolt through the Doctor that he quickly subsided. He leaned against the door of the TARDIS waiting for the ever approaching voices to make their way to the room he had landed in. As the men walked through the door, they stopped and stared in shocked silence. The Doctor immediately answered the questions that were running through their brains.

"Hello, I'm the Doctor," he said. They just looked at each other and the shorter one murmured something to the other one that the Doctor couldn't make out.

The taller one with majestic hair, he assumed was Sam, was the first one to break the silence, "How did you get in here? Who are you?"

"With my TARDIS," the Doctor said, patting the big blue box. That didn't satisfy their curiosity enough because they still looked confused. "And I said, I'm the Doctor. I'm a time traveler, I guess is what you're asking."

"Why are you here, since you don't seem to be trying to kill us," the shorter one-the Doctor figured was Dean-asked in a rude tone, annoying the Doctor. He seemed tense, like there was something bothering him constantly. His eyes looked tired and the Doctor sensed he had interrupted something important.

"You guys are needed in New York and I was sent to come and get you," they didn't seem to buy it, even though it was the truth. "Even if I explain further, you won't believe it until you see it."

This didn't seem to be working. They were only getting more and more curious, more questions being formed as they tried to figure out who he was. A bang came from out of the room, somewhat sounding like a door closing, and the boys looked to each other and then back at the time traveler.

"Stay," Dean said to the Doctor. This just frustrated him further. He decided to stay near his TARDIS, but that didn't mean he wasn't listening and trying to figure out what was going on. The men began talking to another man, who actually had a deeper voice than they did. Footsteps indicated their return to the room and the Doctor had hardly moved, but was incredibly bored. The third man walked in first, brilliant blue eyes blazing. and immediately seemed to recognize him. But the Doctor didn't recognize him back.

"This can't be good," was the first thing he said to him, making the Doctor more curious than either of the boys were about him.

"How do you know me, but I don't know you?"

"I'm an angel," the man said to him and slowly approached the TARDIS. "I have been taught about you, Doctor, and your meddling ways."

"You're an angel?"

"I know all of your faces, this is your twelfth, but you refer to it as your eleventh."

The Doctor was stunned, he replied in a low voice, "How could you possibly know that?" The angel ignored him, but came even closer as he tried to be threatening.

"You will not take these two with you," he said. "Not without me."

"I guess the more the merrier," the Doctor said darkly, realizing there wasn't time to argue. "I didn't catch your name."

"Castiel."

"Alright then," the Doctor opened the door to the TARDIS, then looked back at the trio with another giddy smile. The other two were still confused, but decided to go along with it. "Geronimo."


	5. Chapter 5

"Peggy!" The Doctor walked in quickly before the others walked through and called out so she knew he was coming. "Three more people are going to join us, now."

"Splendid," Peggy replied, slightly bored. Castiel walked through the door first and wasn't shocked by the change of size of the inside of the police box. He just looked around and muttered _Gallifreyans_ under his breath. However, the other two men cautiously stepped inside behind the angel and were shocked by the vastness of the inside of the Doctor's TARDIS.

"Woah," Dean said in awe. Sam just whistled. Then at the same time, the three of them noticed Peggy, who was now standing next to the Doctor. Castiel was in shock, as was Sam, because they both recognized her instantly. Peggy was equally intrigued at the way the men dressed. They were extremely casual and would not have fit in with her time. She then factored in that the Doctor was a time traveler, so they must be from the future. The lack of class saddened her, but yet amused her.

"Please tell what is so interesting about me," she snapped, reminded them she was real and in front of them.

Sam coughed and was the first to speak for the three, "You're... Peggy Carter." The Doctor looked from the trio back to Peggy, thinking about this awkward situation that he accidentally caused and where it could lead. Peggy looked confused and was formulating the best question.

"I probably shouldn't ask this," she started, looking at the Doctor. "How could you possibly know about me?"

Sam sheepishly chuckled and smiled, "I came across you in a book. Is it true that you knew Captain America?" The Doctor cringed and then broke the awkward tension in the room so Peggy wouldn't have to answer that heart shattering question. The men must not have known how she knew him and the circumstances that tore him away from her. So, he began running around the center console and making the TARDIS take off and causing the entire room to shake. The passengers of the TARDIS where thrown about as they arrived at the next place on the list. They all grabbed onto various bars located around the edges of the center console and curses were shouted, by Dean specifically.

"Alright, um, you guys stay here and don't kill each other," the Doctor requested again.

Peggy didn't particularly want to stay "Where are you going now?"

"Last ones to pick up. They're coincidentally not far from each other. I won't keep you lot waiting long."

Grimaces traveled all around the TARDIS at the thought of being caught in this awkward situation. Each individual wanted answers, but they knew the Doctor either didn't have them or couldn't give it to them. Nevertheless, they each kept their similar attitudes to the situation. That being humor where humor can be, with a few punches in between.

The Doctor ran out the door and into the city that never ceased to amaze him. The towering buildings stretched towards the sky, towards the sun and glittering in the light. The sound of people bustling about in mass quantities was another thing that left him in awe. A twinge of sadness, as well, because they all had lives, the one adventure he could never have. He instantly spotted the boy, clad in his backpack and hoodie. He blended in perfectly in the city, looking like everyone else. But the Doctor knew better. He followed him a couple blocks when he saw the girl, wearing different shades of red, who happened to be walking the same direction. He gained distance on them quickly as the boy slowed down, allowing the girl to catch up. Subtly and carefully by cover of the crowd, the Doctor saw the girl slip her hand in the boy's. They walked on as if nothing had changed. The Doctor was in utter shock. They were listed separate and it happened to be a coincidence that they were in the same place at the same time. The Doctor knew better than to believe in coincidences.

Over another block, the Doctor finally made his way closer to the couple, who had released hands but were amid conversation. Then as they walked by an alley, the Doctor felt as if he was suddenly pushed and the next thing he knew, he was on his back in the alley with the two standing over him menacingly.

The girl's eyes and hands glowed a bright red and she asked the Doctor in a thick Russian accent, "Why are you following us?"

The Doctor was getting threatened way too much for his liking in one day. Maybe it was his approach, he'd have to work on that with these people. They were very aggressive, but at least this one wasn't American. Slightly better.

"Well?" The boy, replied in a New York accent, so he must be the one who lived here.

"Peter Parker, Wanda Maximoff…" the Doctor tried to stand up but was pushed down again. "What do you know about the Avengers Initiative?"

Wanda let the Doctor stand up. She and Peter shared a look. Peter was slightly nervous that someone knew to come to him in a time of trouble.

After several long seconds, Wanda finally asked, "What's happened now?"

"And how did you know where to find us," Peter chimed in.

"Steve Rogers and Tony Stark sent me," he said while straightening his bow tie and checking that his sonic screwdriver was still in his pocket. "They said you two would be very useful."

The couple shared another look with each other. Then Peter nodded at her, and she loosened up a bit.

"I'm guessing we're going to the Avengers tower?"

"Yes and if you come with me, I can get you there quickly," the Doctor said with a smirk.


	6. Chapter 6

**A/N: Hello! I haven't done an author's note for this story yet, so I just wanted to thank you all for reading! Hope you enjoy this chapter, it's been my favorite to write so far. :)**

* * *

The Doctor came back to a TARDIS in utter chaos. Dean was clutching his nose and blood dripped through his fingers. Sam and Cas both had a hand on a shoulder, asking if he was okay. Peggy looked very proud of herself but kept stretching out her hand.

"I'm fine, I'm fine. Just get off me," Dean demanded. He glanced up at Peggy and the Doctor stormed into the room, Peter and Wanda in tow. Wanda's attention was immediately drawn to the only other woman in the room, instantly recognizing her, but masking it out of fear. They both looked around in awe as the Doctor glared at his passengers in anger. They thought the Doctor was strange, but seeing this weird bit of technology made them question him further. Peter just wanted to know what everything's function was.

"Oi! What did I say?" Their attention was drawn to the Doctor and his rage. He didn't let anyone respond to his question before he answered it himself, "I said don't kill each other."

"I didn't, Doctor" Peggy asserted. "But maybe next time." She looked Dean in the eyes and said, "Don't touch me again, you useless wanker."

"Peter, Wanda, this is the TARDIS, bigger on the inside smaller on the outside." He made his way over to the console and started pressing buttons. He move a bit too fast for their liking, they were still incredibly confused. "Oh, I forgot, I'm the Doctor, that's Dean, Sam, Castiel, and Peggy. Blimey. Next stop, Avengers Tower!"

Everyone grabbed the bars again as the TARDIS shook around, traveling to its final destination for the time being. None of the passengers of the TARDIS would ever grow used to this method of travel along with the groaning and wheezing it made as it flew throughout time and space. The TARDIS finally landed and the ding made each person's stomach flop. The Doctor gave each one a reassuring smile, especially Peggy, and walked towards the door. He motioned for them all to stay put so he could perform a quick environment check, of the people kind. Outside the TARDIS was a large crowd waiting to greet the new Avengers. He recognized the rest of the original Avengers and some of Coulson's team, excluding Grant Ward, Agent May, and Coulson himself. The Doctor looked at Steve and saw several emotions cross his face. He longed for Peggy but dreaded to see her. Fifty shades of worry crossed his face in a single second.

"Alright, I got them all," the Doctor said cautiously. He looked back inside. "Come on out guys, the water's fine."

They each exited the TARDIS, one by one. First Wanda and Peter, then Sam, Dean, and Cas. Peggy was too consumed by anxiety to leave and didn't move an inch from her spot near the console. Her stomach churned due to her nerves. The Doctor sent an apologetic look at the group and ran inside when he noticed she wasn't leaving. Cas was the first to introduce himself to the group.

"I'm Castiel."

Tony snorted and instantly retorted, "Is that your stripper name?" Sam burst out laughing and Dean just smirked.

"No I'm an angel."

Skye Johnson, Jemma Simmons, and Leo Fitz had been standing at the front of the group watching everything play out. Skye wanted to know more about the strangers and the strange man claiming to be something impossible. She reminded herself about what she was, and not to be so close-minded.

"You're an angel? Figuratively or literally?" Tony looked over at the girl who had arrived in his tower not even half an hour ago with nothing but respect. Castiel was confused.

"I am not a male entertainment star." Cas slightly blushed and his friends behind him bit back more laughter. "I don't see how this is of importance, what we need to focusing on is-"

Tony interrupted, "So how long have you been banging your friend back there?" Dean was taken aback, as was Cas who also blushed. Sam looked at his brother, who couldn't find the words to say to defend himself then back at the angel.

Skye redirected the conversation, "Do you have wings?"

"Well," Castiel was starting to regret introducing himself first. "Yes, but if I showed you, you would all die, which isn't sounding like a bad idea at the moment."

"If you do any flying, please be sure not to fly out the window," Tony said pointedly, looking at Sam Wilson. "I've been having problems with that here lately."

Clint smirked from his perch on the stairs above the floor where the group had collected around the TARDIS.

"I don't fly anymore thanks to Metatron," Cas stated sadly.

Skye felt bad but questioned further, "A transformer clipped your wings?"

Sam choked on air and she noticed the large man for the first time. He gave her a small smile respecting her comment that he had also made awhile ago when first hearing of Metatron himself.

Fitz had been silent the entire conversation, calculating everything, but he perked up at the mention of something he knew, "No, uh, Metatron is the scribe of God, I believe."

Cas, Sam, and Dean all looked at Fitz with an odd look, as he shrunk a bit at the attention. Skye and Simmons glared back in silent defence of the boy and the men looked away.

"What's a transformer?" Steve whispered to Natasha.

Thor was confused as well, "How does one transform?"

"I'll explain later," Natasha snapped to both of them.

"We have not been properly acquainted, angel Castle," Thor said. "Who are these fleece clad warriors? I also see the Witch of Scarlet but who is this other man with her?"

Cas half-ignored him, Wanda smiled at the mention of her name and Peter began to introduce himself, before Cas starting walking closer to the group, fully noticing the it for the first time and recognizing some. "It's Castiel." He approached Steve and Natasha who were standing next to each other. He analyzed Steve's face and realized, "You're that American Captain."

"It's Captain America," Steve corrected.

"Rude," Natasha muttered under her breath. Cas moved over to her and her reflexes told her to attack the man who was definitely invading her personal space, but she resisted. Everyone was still shocked at the erratic behavior the man was displaying. He analyzed her curiously and also realized who she was.

"You don't find yourself worthy to be here," he gently stated. She didn't like where this was headed. "You don't think you're worthy of being saved."

As Cas reached up and touched Natasha's forehead, she flinched as she felt the hole inside of her be filled with a new warmth. She finally felt human and had a small sense of belonging. Sam stepped in, not realizing what the angel had done for her, and made him step away.

"Alright buddy, they're taking this all in stride." Sam said. "Let's ease up on the healing for today."

Natasha stared at him, "How did you do that?"

"Like I said," Cas said with a small smile. "I'm an angel of the Lord."


	7. Chapter 7

As Steve Rogers looked around the room, his anxiety peaked. Peggy was one of the biggest people they wanted to bring here due to her extensive knowledge of the Shadow.

...so where was she?

Back inside the TARDIS, the Doctor walked over to the woman out of her time and sensed her anxiety and her sadness. The pain at losing a lost love and the worry of the love being gone. It radiated from her in waves. It hurt his heart.

"He's out there isn't he?" Peggy asked deadfaced. There wasn't an emotion showing on her face. Nothing but her default stoic expression that seemed to hide her true emotions. The Doctor knew better.

"He's been waiting for you Peggy," he said with a small smile. However, she didn't move. Didn't reply. Her stoic manner was holding back a dam of emotion, and one tear leaked through and slipped down her face. He knew her pride, but had a kind heart. His hand found her shoulder, then her hand. "Come on."

With a subtle jaw clench, her legs worked against her will. The Doctor led her to the door and placed his hand on the handle, sending her stomach to the floor and her heart to her throat. Unexpectedly, the Doctor paused and asked her, "Are you ready? He's right outside." With a deep breath, she nodded and the door opened. Everyone in the room was arguing and talking to the three men she had earlier met, unsurprisingly, but then she laid eyes on him. The conversation faded out to a low hum. He had hardly changed a bit, but she could see pain in his eyes. But he was the same Steve that had kissed her all those years ago. The same Steve that jumped on a grenade during training. The same Steve that promised her to meet her at the Stork Club for a dance. The same Steve that never showed up. The same Steve who was lost to her in her time.

He locked eyes with her. Everyone in the room noticed her for the first time and a few looked amazed to see her, which she hardly noticed, her focus being on Steve. The room went quiet with anticipation. They both were fixed where they stood, in shock. They remained that way for several heart wrenching seconds. Then Steve broke from his spot across the room, the silence still booming in his ears, and made his way to the girl standing in the doorway of the blue box. Peggy followed suit, and the two ran to each other and embraced each other for the first time in years. Every remained transfixed, looking at the reunion of the two that had been separated over 70 years ago. Neither said a word, they just breathed in the familiar scent of each other.

"Steve," Peggy said, gripping Steve harder and holding back a river of tears. But they flowed anyway, as he was one of her only weaknesses. Even Steve was crying. He never thought he would get to see her again looking like she had when they first met. Everyone in the room was silent except Sam Winchester who let out a long "oh" realizing that when he had asked her about the Captain, it was thoughtless. She had just lost him. Jemma Simmons was off fangirling in the corner, only noticed by Leo Fitz and Skye.

"Sorry to break up the reunion, but we do have a pressing matter at hand," Tony Stark stated a bit insensitively. The comment flared a small rage in Peggy's stomach, knowing the voice that it came from. She let go of Steve batted away her tears and faced the man.

"Howard Sta-" she started, but was cut short at the similar looking man in front of her. "Wait, who are you?"

"Howard Stark's son, Tony."

"You look and act just like him," she said with a laugh. Then made a realization. "Wow, what year is it?"

Steve piped up and answered, "2015."

"I fear for the future."

Everyone in the room laughed or smiled at Peggy's remark, except Tony who gave a joking glare. Then retorted, "Are you dating that waitress, yet?" Steve looked very confused, as did everyone else in the room.

"You're as much of an ass as your father, Tony."

"Even young, you're the most stubborn woman I've ever met."

"Touche."

"Good to see you, Aunt Peggy," Tony said. Peggy just smirked.

"So why gather us?" Dean interrupted. Everyone's attention turned to him and he became a bit uncomfortable. Tony grabbed a manilla folder off the counter he had been leaning against. On it was a big "A" with the word "expansion" below in thick black letters.

"This is the Avengers Expansion folder," Tony answered "A list of people who can help us against a big evil."

"What are we up against?" Sam asked.

"She's called the Shadow," the Doctor walked into the room. He smirked, realizing that he had the center of attention. He basked in it. "You're here because you have skills that we can use."

"Is she an angel...or a demon?"

"No, but she has an army," the Doctor said. He closed the door to the TARDIS and leaned against it, crossing his legs. "You can bet your flannel shirt collection that there will be angels and demons."

Peggy remembered the Shadow and shuddered at the memory of her. With a dark look, she asked in a low voice, "She's back?"

"What can you tell us about her?" Tony said. "What's her play?"

"Well now I know why I'm here," Peggy said bitterly, running her hand through her hair. "But I'm sorry to tell you that I don't remember much about her for some reason. It's all a bit fuzzy. I remember where she is contained and that she hates men, but that's about it."

The Doctor looked down at his feet, remembering when she had almost died so long ago. He still respected her actions and wanted to tell her, but he knew he couldn't. So he remained waiting for them all to get to work against their old enemy. The large group wasn't quite sure what to do; there was an awkward tension among them.

Steve took charge and faced the group saying, "Well let's get to work."

* * *

 **A/N: Hello! Sorry for making you wait for so long for this chapter. I was trying to make the steggy reunion the best I could. *sobbing* Hoped you liked it and thanks for 1,000 views!**


	8. Chapter 8

**Okay. I'm sorry for the _VERY_ long wait I have made some of you endure. I'm just going to admit it... **

**I had writer's block.**

 **I knew where I wanted to go, but I wasn't sure how to get there. So here we are! Some plot advancement! Yay!**

 **I hope you enjoy this chapter, thank you for reading!**

* * *

 _Crumbling. Crackling._ The sound of fire consuming and rubble moving was all Peggy heard when she forced her eyes open. The last thing she remembered was looking at Steve's determined face, aged slightly since she last saw him, but only slightly. His eyes gave away his age. Sadness was laced into that blue that she had longed to see for what seemed like ages to her, but had only been a couple years compared to his 50. The only thing she remembered after his call for action, was only black.

Peggy looked around her, smelling the air for a source of the blast but only could smell a strange rotten egg smell. She began to move her body, each individual muscle aching and burning. She tried in vain, but could only manage to move her arms. Her hand began to feel the rubble next to her, her eyes still straining to fully see what was around her. All she felt was rock and metal, which she carefully ran her hand over as to not potentially cut herself. She felt only stone and metal, but then she felt a warm and smooth surface, that was definitely alive as it slightly moved at her touch. She looked over, her eyes beginning to clear, and saw the girl, Skye she believed she was called, lying next to her with a gash across her forehead but still alive regardless. She looked down at her hand, which was near the hers, reached it and squeezed gently as to get her attention.

"Skye," Peggy weakly said, surprising herself with her hoarse voice. "Are you alright?"

Skye only groaned in response, her body barely moving at all. She let go of her hand and began looking around the space she was in with her cleared eyes. Bits of rubble fell from the ceiling to the ground and falling down the mountains of siding that had gathered in the room. Observing the room in its entirety, she noticed the doorways were blocked and she located the others. They were scattered around, some only just coming to as Peggy had and noticing the disaster struck room around them.

Steve had been barely affected by the blast and was tending to someone that she couldn't see through the rubble. Sitting up, she realized her body was essentially unharmed, just sore from being thrown across the room.

 _Obviously_ , Peggy thought to herself.

She stood up, a bit shakily, but she began to walk over and assess the rest of the damage.

"Son of a bitch," Dean hoarsely moaned. Peggy's head snapped over and noticed that he, Sam, and the "angel" had been thrown right at her feet. He rubbed his eyes with the heel of his hand. "What was _that_?"

Scornfully, Peggy glared down at him, but also with a twinge of boredom in her expression. Sighing, she then said, "What do you think it was?"

"It was the Shadow," the angel, Castiel said, opening his eyes and finally coming to. He sat straight up and pulled himself into a standing position, dusting off his jacket a bit on the shoulders where bits of rubble had collected. The entire event left him unfazed. Peggy stared at him like he had grown a second head. As Dean opened his mouth to make a comment on his boyfriend's behalf, there was the sound of a crash outside the blocked room. Everyone else that had slowly been waking up and coming back to consciousness shot straight up. Natasha had sprung up ready to fight anything and nearly floored the person in front of her, which just so happened to have been Clint, unfortunately for him. Surprisingly, no one had been seriously injured, but they all had one hell of a headache.

The crashing continued and grew louder, signifying it was growing closer. It grew louder and louder, prompting those standing to start to help those on the ground to their feet and bring them to the middle where everyone began to stand back to back in a circle. They each were ready, in their signature fighting stances. Steve had found his shield, dusted off the bits of glass and dirt from it and held it in his hand. Feeling naked without her gun, Peggy had picked up a pipe that was laying on the ground amidst the rubble from the blast. Skye had finally come to, her gash not being as deep as it seemed, but blood still dripping down her nose. She was slightly woozy but Fitz and Simmons stood on either side for support. Wanda and Peter stood next to each other and the rest of the avengers, as well. As the crashing finally grew to as loud as it possibly could, it ceased. The circle stood motionless and silent, waiting for whatever was to come. Each could somewhat hear something from the other side of the wall, but it was unclear if it was a person...or thing, or just bits of the building falling.

"Huh," Dean said, breaking the silence. "Maybe it-"

A loud crash interrupted him, a big hole being formed in the wall that he was facing accompanying the sound. Through the hole came a very distressed Doctor, that was missing his iconic tweed jacket. His shirt was covered in ashes with holes burned through in places. His hair was a mess, contrasting the neat and artistically messy hair everyone had saw him with only an hour or so earlier. He landed on the floor, rolling to take out the impact of the fall. Stopping on his back, he caught his breath and closed his eyes as his hearts raced.

"Um, Doctor?" Peggy asked, really confused about what just happened, along with the many others in the room.

"Yeah, yeah, you're probably wondering what the hell I was just running from," the Doctor said breathlessly. He took one deep breath and stood up quickly with a smile. "Good question, well, you see I woke up in the TARDIS, which has gone through the floor for some odd reason, and I knew I had to make my way back up here. I found the stairwell through this mess of a building, speaking of which, do you know how _boring_ stairwells are? I quite prefer a-"

"Doctor." Peggy asserted, prompting him to get to the point.

"Oh yes, sorry, got off on a tangent. Where was I? Oh! I got to the top of the stairs and I saw a black smoke approach me. It filled my nose and it burned as it filled my body. It realized how much bigger on the inside I was, how massively complex my brain was compared to humans. I fought this smoke, it was more than just smoke, it seemed sentient, as if it were alive and capable of thought. I battled it, I'm surprisingly familiar with internal battles for my brain, so the concept and strategies weren't new to me."

The Doctor's speech was increasingly making everyone uncomfortable. He seemed too alright, too okay for someone who had fallen through the floor and had seemingly been burned. He looked like he had gone through hell, but he didn't feel a thing. Sam and Dean grew very suspicious at the mention of black smoke. They kept looking at each other while the Doctor was talking, but he never noticed.

The Doctor continued, "I talked to the black smoke, it was actually a quite intelligent conversation. But then I learned the smoke's true name. In fact, it wasn't smoke at all, it was just a temporary form."

"Doctor," Dean moved towards him slowly, with a concerned expression on his face. His sudden seriousness and taking over for the group was new to everyone, but they quickly accepted it. "What was the smoke?

"You know, at first I thought it was a demon. I wasn't worried, demons are normal and are actually all around the world. I knew they could only inhabit human bodies, but that I would still have to cast them out as one does swat a fly. But the battle wasn't easy, and I grew weaker by the second."

Peggy looked to Steve with a worried expression, then stepped up next to Dean. She asked, "Then what was it?"

The Doctor blinked, his eyes switching to a complete and absolute black. Everyone backed away slowly from him, the few with weapons gripping them tighter in anticipation of an attack. The Doctor smirked and his carefree expression that he always wore turned dark as night.

"I call myself the Shadow."


End file.
